1. Field of the Invention
Embodiments described herein relate generally to a magnetic resonance diagnosis apparatus and a data acquisition method of magnetic resonance spectroscopy.
2. Description of the Related Art
MRI is an imaging method which magnetically excites nuclear spin of an object (a patient) set in a static magnetic field with an RF pulse having the Larmor frequency and reconstructs an image based on MR signals generated due to the excitation. The aforementioned MRI means magnetic resonance imaging, the RF pulse means a radio frequency pulse, and the MR signal means a nuclear magnetic resonance signal.
In MRI, if an intensity ratio of concentration distribution of metabolic substance such as choline, creatine and NAA (N-acetylaspartate) changes due to, for example, tumor or hemorrhage, information of tumor or hemorrhage cannot be obtained.
Meanwhile, as a technology to visually capture category and concentration distribution of metabolic substance which cannot be obtained from images of MRI, MRS (magnetic resonance spectroscopy, refer to Japanese Publication of Patent Application No. 2009-279432, for example) is known.
MRS is a disuniting method in which signals of respective molecules are individually extracted based on “chemical shift”. The chemical shift is difference of magnetic resonance frequency between various molecules caused by difference of chemical bonds of the various molecules.
As a contributing factor of artifact in MRS, “commingling of water signals and a fat signals” and “non-uniformity of static magnetic field” are included.
Specifically, for example, when a region of interest is parenchyma of the brain, a static magnetic field becomes non-uniform “near a part which contains much wet such as cerebrospinal fluid” and “near a part which contains air such as a nasal cavity, auditory canal and bony canal”. This is because parenchyma of the brain is different in magnetic susceptibility from “regions near a part containing air or much wet”.
If a static magnetic field becomes non-uniform, half bandwidth of a peak of a metabolic substance becomes wider. This disables disuniting of respective peaks of a plurality of metabolic substances whose chemical shifts are close to each other, or causes commingling of undesired signals from outside of a data acquisition region.
Additionally, if strong MR signals of water or fat are mixed, this makes it difficult to detect respective peaks of metabolic substances whose chemical shifts are close to water or fat. This is because signals of metabolic substances are weak.
Then, in order to suppress MR signals from parts which cause artifact in MRS, technology of applying a presaturation pulse before data acquisition of MRS is known. A presaturation pulse is a prepulse which spatially selectively saturates MR signals of its application region.
In the above prior technology, an operator sets an application region of a presaturation pulse which saturates MR signals of parts including air, water and fat, aside from setting of acquisition region of MR signals in MRS.
Therefore, “technology to ease operator's labor required for setting of data acquisition conditions such as an application region of a prepulse and an acquisition region of MR signals when MRS is performed, by making the setting of the data acquisition conditions easier than prior art” has been desired.